How to query several similar databases using Peewee?

问题

I'm stuck with a problem about querying multiple databases using Peewee:

I have 2 existing mysql databases (let's name them A and B) (Structures are similar because it's two Bugzilla databases)
I generate models (modelsA.py and modelsB.py) using Pwiz
I write this code:

from modelsA import *
from modelsB import *

The problem is: as the classes in modelsB are (sometimes) the same than modelsA, modelsB classes "overwrite" modelsA classes, making impossible to query A.

Besides, I don't understand how to query one of the specific database. For example, with this code:

c = Customers.get(Customers.customernumber == 12)

How do you know on which database this query is gonna be executed?

I had an idea, but it seems dirty to me: I could manually rename classes from modelsA.py and modelsB.py to make them distincts and then write this code:

ca = CustomersA.get(CustomersA.customernumber == 12)
cb = CustomersB.get(CustomersB.customernumber == 12)

Roughly, is Peewee able to deal with these kind of cases? If so, what is the way to do? Snippets would be very appreciated ^^ Thanks.

回答1:

Next is maybe not exact an answer to your problem, but what I tried myself - succesfully - is using a playhouse.Proxy instance for every schema I want to use, and refer to a corresponding proxy in the innerclass Meta. I guess this will work without proxies too. However, seems you are looking for cross-schema queries, and already figured out what I came up with just now.

#!/usr/bin/python

import sqlite3
import peewee
from peewee import *
from playhouse.proxy import *

database_a_proxy = Proxy()
database_b_proxy = Proxy()

class BaseModelA(Model):
    class Meta:
            database = database_a_proxy

class BaseModelB(Model):
    class Meta:
            database = database_b_proxy

class RelationInSchemaA(BaseModelA):
    textfield = CharField()

class RelationInSchemaB(BaseModelB):
    textfield = CharField()

database_a = SqliteDatabase('schemaA', **{})
database_b = SqliteDatabase('schemaB', **{})

database_a_proxy.initialize(database_a)
database_b_proxy.initialize(database_b)

try:
   RelationInSchemaA.create_table()
   RelationInSchemaB.create_table()
except:
   pass

RelationInSchemaA.create(textfield='Hello')  
RelationInSchemaB.create(textfield='PeeWee')

Well, this is possible with handcrafting generated code from pwiz.py. I am sure there is a more elegant and lazy (i.e. not eager) way to do this, too, using some kind of factory, but I did not spend much time on Python nor PeeWee yet. If so, pwiz.py should have an extra flag for this purpose too, I guess.

回答2:

I think this way is simpler:

import modelsA as A
import modelsB as B

ca = A.Customers.get(A.Customers.customernumber == 12)
cb = B.Customers.get(B.Customers.customernumber == 12)

来源：https://stackoverflow.com/questions/20003916/how-to-query-several-similar-databases-using-peewee

标签

python

mysql

orm

peewee